JP2000322994A - Alloy-type temperature fuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adequately provide an operation at a prescribed upper limit temperature and an operation at a prescribed over current at temperature lower than this upper limit temperature, by providing a notch in a low-melting-point fusible alloy piece as a fuse element coated with flux. SOLUTION: A notch 30 is provided in the longitudinal center part of a low-melting-point fusible alloy piece 3 as a fuse element. A melting point of the low-melting-point fusible alloy piece 3 is set according to an upper limit temperature (tolerance temperature) of an electronic/electric apparatus to be protected, the low-melting-point fusible alloy piece 3 is melted when temperature of the apparatus reaches the upper limit temperature by any cause, an active operation or a wet accelerating operation of already melted flux 4 accelerates spheroidizing disconnection of the melted alloy, and the disconnection cuts off carrying a current to the apparatus. When a prescribed over current flows through the apparatus by any cause even at temperature less than the upper limit temperature of the apparatus, the over current fuses the notch 30 in the low-melting-point fusible alloy piece 3 with Joule heating to cut off carrying a current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy type temperature fuse which can be quickly operated even with a predetermined overcurrent, and is useful for protecting a secondary battery such as a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, portable telephones, PHSs and portable parsers have been developed.
As a power source for portable electronic devices such as a personal computer, a battery that can be repeatedly charged and discharged, that is, a secondary battery, is frequently used. Among them, a lithium ion secondary battery has a high energy density, a long cycle life, and a low It is mainstream due to its self-discharge property and high operating voltage. However, due to the high energy density of the lithium ion secondary battery, if an internal short circuit occurs for any reason, the energy is released at once and the battery may explode due to abnormally high temperature. It has been practiced to incorporate a temperature fuse to shut off a battery circuit at a predetermined upper limit temperature before reaching an abnormally high temperature. In this case, if the alloy type temperature fuse is designed to operate even at a predetermined overcurrent, and the predetermined overcurrent flows below the upper limit temperature, the battery circuit is cut off by the overcurrent. It is possible to further enhance safety.

[0003]

It is necessary to interrupt the overcurrent as quickly as possible (if the time until the interruption is prolonged, the temperature rises during that time until the temperature approaches the upper limit temperature). And the significance of the overcurrent interruption is lost), which requires an increase in the resistance value of the fuse element. However, when the resistance value of the low melting point fusible alloy piece of the alloy type temperature fuse is increased, the self-heating due to the normal current of the low melting point fusible alloy piece becomes remarkable, and the low melting point fusible alloy piece in the normal state is increased. temperature is higher than the normal case (the higher becomes the temperature and [Delta] T), the upper limit temperature (T _x) lower than the temperature (T _x -.DELTA.T) alloy type thermal fuse -'s ends up working In addition, the operating accuracy of the alloy type temperature fuse is significantly reduced.

[0004] It is an object of the present invention to provide an alloy type temperature heater capable of operating at a predetermined upper limit temperature and operating at a predetermined overcurrent at a temperature lower than the upper limit temperature. To provide

[0005]

SUMMARY OF THE INVENTION An alloy type temperature fuse according to the present invention is a temperature fuse in which a low melting point fusible alloy piece coated with a flux is used as a fuse element and is operated even at a predetermined overcurrent. The cross-sectional area S ′ of the notch is 0.1 S ≦ S ′ ≦ 0.8 S with respect to the cross-sectional area S of the non-notch. The length L 'of the notch is the effective length L of the low melting point fusible alloy piece.
0.02L ≦ L ′ ≦ 0.80L, the sectional area S is 0.0078 to 3.5 mm ^2, and the effective length L is 0.5 to 5.0 mm. Further, the notch can be asymmetrical with respect to the center line of the low melting point fusible alloy piece, the melting point of the low melting point fusible alloy piece is in the range of 50 ° C to 200 ° C, The resistance value is in the range of 0.1 to 400 mΩ.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a drawing showing an example of an alloy-type temperature fuse according to the present invention, and FIG. 1B is a cross-sectional view taken along a line in FIG. In FIG. 1, 1 is a plastic base film, 2, 2
Is a pair of strip-shaped lead conductors, which can be fixed to the base film 1 by fusion or an adhesive. 3 is Lee
A ribbon-shaped low melting point fusible alloy piece as a fuse element connected by welding between the conductors 2 and 2, and a notch 30 is provided at the center in the longitudinal direction. Reference numeral 4 denotes a flux applied to the low melting point fusible alloy piece 3. Reference numeral 5 denotes a plastic cover film.
Sealed by sealing, high frequency welding, ultrasonic welding or adhesive.

In FIG. 1, S is the cross-sectional area of the low melting point fusible alloy piece, S 'is the cross-sectional area of the notch, h is the thickness of the low melting point fusible alloy piece, and L is the low melting point fusible alloy piece. , And L ′ indicates the length of the notch.

[0008] The melting point of the low melting point fusible alloy piece is set according to the upper limit temperature (allowable temperature) of the electronic / electrical equipment to be protected, for example, the secondary battery, and when the equipment reaches the upper limit temperature for some reason. The low-melting-point fusible alloy piece is melted, and the spheroidization of the molten alloy is promoted by the activation action and the wetting promotion action of the already-melted flux, which cuts off the power supply to the equipment.

Also, even when the temperature is below the upper limit temperature of the device, if a predetermined overcurrent flows through the device for some reason, the cutout of the low melting point fusible alloy piece is cut off by Joule heat due to the overcurrent. Power supply is cut off. In this case, the overcurrent flows instantaneously, the notch portion instantaneously generates heat, and only the notch portion of the low melting point fusible alloy piece is instantaneously heated to the melting point and melted. The time until the portion is melted can be made sufficiently shorter than the case where the entire low melting point fusible alloy piece is heated to the melting point and melted without the notch. Therefore, the overcurrent can be cut off in a short time.

On the other hand, a notch is provided in the low melting point fusible alloy piece.
This increases the resistance of the low melting point fusible alloy piece,
The heat generated in the notch due to the time current is applied to the entire low melting point fusible alloy piece.
Is diffused enough to reduce the intensive temperature rise in the notch?
Temperature rise ΔT of low melting point fusible alloy piece due to normal current
Can be made sufficiently small. In the above, low melting point fusible alloy piece
The melting point of_mIf this happens, the heat generated by the equipment will
The temperature of the low melting point fusible alloy piece is (T_m-T₀−Δ
When the temperature is increased by (T), (T₀Is normal temperature), the temperature fuse is
To work. Thus, the equipment and alloy mold temperature fuse
The temperature difference between the low melting point fusible alloy piece and ΔT_mAs the equipment
If the temperature is (T _m+ ΔT_m-T₀-ΔT)
That is, if the device temperature is (T_m+ ΔT_m-ΔT)
And the operation of the temperature fuse cuts off the power to the equipment.
Is done. As described above, ΔT can be made sufficiently small.
The upper limit temperature T of the equipment_xOf low melting point fusible alloy
Melting point T_mTo (T_x−ΔT_m)
Equipment can be prevented from exceeding the upper limit temperature and equipment is properly protected.
it can.

Therefore, according to the alloy type temperature fuse of the present invention, the equipment can be properly protected against both the upper limit temperature and the overcurrent.

The alloy type temperature fuse according to the present invention can be used for protecting secondary batteries, for example, lithium ion secondary batteries, lithium polymer secondary batteries, nickel-cadmium secondary batteries, nickel-hydrogen secondary batteries, and the like. In this case, the melting point of the low melting point fusible alloy piece is 50 ° C to 200 ° C, preferably 80 ° C to
It is set within the range of 150 ° C., and the resistance value of the low melting point fusible alloy piece is 0.1 mΩ to 400 mΩ, preferably 0.5 mΩ to
It is set within the range of 20 mΩ.

In the case of a battery, the low melting point fusible alloy piece has a sectional area S of 0.0078 to 3.5 mm ² , an effective length L of 0.5 to 5.0 mm, and a sectional area of the notch. S ′ is 0.1S ≦ S ′ ≦ 0.8S with respect to the cross-sectional area S, and the length L ′ of the notch is 0.02L ≦ L ′ ≦ 0.80 with respect to the effective length L.
L. 0.1S ≦ S ′ ≦ 0.8S
If it is less than 0.1, it is easy to break at the notch, and if it exceeds 0.8, it is difficult to satisfactorily achieve the rapid interruption of overcurrent due to instantaneous heat generation and fusing of the notch.
When L ′ ≦ 0.80 L, if it is less than 0.02, re-conduction occurs in the cutout portion that has been melted, and it is difficult to reliably shut off the cutout portion.
If it exceeds 0.8, it is difficult to satisfactorily achieve the rapid interruption of the overcurrent similarly to the above.

In the present invention, the notches are symmetrical and asymmetrical with respect to the center line of the low melting point fusible alloy piece, as in the ribbon-like low melting point fusible alloy piece shown in FIGS. 2 (a) to 2 (g). However, in the case of an asymmetric structure, it is difficult to cause heat diffusion along the low melting point fusible alloy piece around the notch portion for instantaneous heat generation of the notch portion. Since the overcurrent cutoff speed can be increased by increasing the speed, it is preferable to provide an asymmetrical configuration as shown in FIGS. As shown in FIGS. 2F and 2G, a plurality of notches can be provided so as to be shifted in the longitudinal direction. In this case, each of the notches has the above-mentioned condition: 0.1S ≦ S ′ ≦
0.8S and 0.02L ≦ L ′ ≦ 0.80L can be satisfied.

In the above embodiment, the low melting point fusible alloy piece has a ribbon shape, but may have a round cross section.

The alloy type temperature fuse according to the present invention is suitable as a protector for a secondary battery, is in close contact with the battery can, and is electrically connected in series between the positive and negative electrodes of the battery. It can be inserted and used.

FIGS. 3 (a) and 3 (b) [a cross-sectional view taken along a roll of FIG. 3 (a)] show another example of the alloy type temperature fuse according to the present invention. The leading end of the lead conductor 2 is squeezed, and the squeezing projection 20 is exposed from the back side to the front side of the base film 1 in a watertight manner, and the low melting point fusible alloy piece 3 with the notch 30 is squeezed out. The low melting point fusible alloy piece 3 is connected to the projections 20 by welding.
The peripheral portion of the cover film 5 is sealed to the base film 1 by heat sealing, high frequency welding, ultrasonic welding or an adhesive.

In the above embodiment according to the present invention, the base film 1 and the cover film 5 have a thickness of 4 μm to 35 μm.
0 μm heat-resistant plastic film, for example, polyimide film, ABS resin film, polyethylene terephthalate film, polysulfide film, polycarbonate film, polypropylene film, polyamide film, polyethylene film, etc. can be used,
As the lead conductor 2, a nickel conductor, a copper conductor, an aluminum conductor, a copper-plated iron conductor, or the like can be used.

The plane size of the alloy-type temperature fuse body according to the present invention is usually (1.0 to 4.0 mm) × (5.0 to 1).
5.0 mm).

[0020]

Embodiment 1 In FIG. 1, a low melting point alloy having a melting point (solidus temperature) of 92 ° C. was used as a low melting point fusible alloy piece.
The cross-sectional area S is 0.080 mm ² , and the cross-sectional area S ′ of the notch is
Was set to 0.024 mm ² (accordingly, S ′ / S = 0.3), the effective length L was set to 2.0 mm, and the length L ′ of the notch was set to 0.4 mm (according to L ′ / L). The base film and the cover film have a length of 8.0 mm, a width of 3.0 mm, and a thickness of 100 mm.
A μm polyethylene terephthalate film was used. FIG. 4 shows the current fusing characteristics of the product of this example. When the resistance was measured, it was 1
It was 0.4 mΩ.

Example 2 Cross-sectional area S of low melting point fusible alloy piece
Is 0.123 mm ² , and the cross-sectional area S ′ of the notch is 0.036
Example 2 was the same as Example 1 except that mm ² (accordingly, S ′ / S = 0.3). The current fusing characteristics of this example were measured, as shown in FIG. 4, and the resistance was measured to be 8.0 mΩ.

Example 3 Cross-sectional area S of low melting point fusible alloy piece
Is 0.123 mm ² , and the cross-sectional area S ′ of the notch is 0.036
mm ² (thus S ′ / S = 0.3) and the effective length L is 2.0
mm, the length L ′ of the notch is 0.8 mm (therefore, L ′ /
L) and the same as Example 1. The current fusing characteristics of the product of this example were measured, as shown in FIG.
When the resistance value was measured, it was 9.6 mΩ.

Comparative Example 1 The same procedure as in Example 1 was performed except that the notch was omitted. The current fusing characteristics of this comparative example were measured and are shown in FIG.
When the resistance value was measured, it was 8.0 mΩ.

Comparative Example 2 Comparative Example 1 was the same as Comparative Example 1 except that the thickness of the low melting point fusible alloy piece was reduced to half. The current fusing characteristics of this comparative example were measured, as shown in FIG. 4, and the resistance was measured.
It was 2 mΩ.

[0025]

Table 1 Table 1 Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 S (mm) 0.080 0.040 0.080 0.123 0.123 S '(mm)--0.024 0.036 0.036 S '/ S--0.3 0.3 0.3 L (mm) 2.0 2.0 2.0 2.0 2.0 2.0 L' (mm)--0.4 0.4 0.8 L '/ L --- 0.2 0.2 0.4 0.4 A Interruption time at 40 A t 0.34 t 0.20 t 0.18 t 0.25 t Resistance r 1.9r 1.3r 1. 0r 1.2r

As shown in Comparative Example 1 and Comparative Example 2 in Table 1, the cross-sectional area S of the low melting point fusible alloy piece was reduced without providing a notch in the low melting point fusible alloy piece, and the overcurrent (40 A ) When the cut-off time for () is reduced.
In contrast to Examples 1 to 3, with respect to the increase in the resistance value (increased by 1.9 times) and the increase in the resistance value (increased by 1.9 times), according to the present invention, the cutoff time of the overcurrent can be further reduced and the resistance can be reduced. The increase in the value can be suppressed. Therefore, according to the alloy type temperature fuse of the present invention, the overcurrent can be quickly cut off, the equipment can be properly protected from the overcurrent, and the temperature rise ΔT of the low melting point fusible alloy piece due to the normal current. And protect the equipment from abnormal heating properly.

[0027]

According to the alloy type temperature fuse of the present invention, the device is operated at a predetermined upper limit temperature, and is operated at a predetermined overcurrent at a temperature lower than the upper limit temperature. Can be performed accurately, and the secondary battery can be well protected from both the temperature and the electric current. This is particularly useful for safe use of a lithium ion secondary battery having a high energy density.

[Brief description of the drawings]

FIG. 1 is a drawing showing an example of an alloy type temperature fuse according to the present invention.

FIG. 2 is a drawing showing different shapes of notches of a low melting point fusible alloy piece according to the present invention.

FIG. 3 is a drawing showing another example of the alloy type temperature fuse according to the present invention.

FIG. 4 is a drawing showing current fusing characteristics of an example of the present invention and a comparative example.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 31, 1999 (1999.5.3
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

As shown in Comparative Example 1 and Comparative Example 2 in Table 1, the cross-sectional area S of the low melting point fusible alloy piece was reduced without providing a notch in the low melting point fusible alloy piece, and the overcurrent (40 A ) When the cut-off time for () is reduced.
In contrast to Examples 1 to 3, in contrast to the increase in the resistance value (increased by 1.9 times) and the increase in the resistance value (increased by 1.9 times), according to the present invention, the cutoff time of the overcurrent can be further reduced and the resistance can be reduced. The increase in the value can be suppressed. Therefore, according to the alloy type temperature fuse according to the present invention, the overcurrent can be quickly cut off, the equipment can be properly protected from the overcurrent, and the temperature rise ΔT of the low melting point fusible alloy piece due to the normal current. And protect the equipment from abnormal heating properly. ────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 12, 1999 (1999.7.1)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

As shown in Comparative Example 1 and Comparative Example 2 in Table 1, the cross-sectional area S of the low melting point fusible alloy piece was reduced without providing a notch in the low melting point fusible alloy piece, and the overcurrent (40 A ) When the cut-off time is shortened ( Table 1)
As can be seen from Examples 1 to 3, with respect to the increase in resistance value (increased by 1.9 times) and the increase in resistance value (increased by 1.9 times), according to the present invention, the cutoff time of overcurrent is increased. It is possible to reduce the resistance and suppress an increase in the resistance value. Therefore,
ADVANTAGE OF THE INVENTION According to the alloy type temperature fuse which concerns on this invention, an overcurrent can be interrupted quickly, an apparatus can be protected accurately from an overcurrent, and the temperature rise (DELTA) T of the low melting point fusible alloy piece by normal current can be improved. It can protect the equipment from abnormal heating properly.

Claims (5)

[Claims] The present invention is a temperature fuse operated by a low melting point fusible alloy piece coated with a flux as a fuse element and operating at a predetermined overcurrent. The low melting point fusible alloy piece is provided with a notch. Characteristic alloy type temperature fuse. 2. The sectional area S 'of the notch is changed to the sectional area S' of the non-notch.
0.1S ≦ S ′ ≦ 0.8S, and the length L ′ of the notch is 0.02L ≦ the effective length L of the low melting point fusible alloy piece.
L ′ ≦ 0.80 L, and the cross-sectional area S is 0.0078 to
And 3.5 mm ^2, according to claim 1, wherein the effective length L was 0.5~5.0mm alloy type thermal fuse -'s. 3. The alloy type temperature fuse according to claim 1, wherein the notch is asymmetric with respect to the center line of the low melting point fusible alloy piece. 4. The melting point of the low melting point fusible alloy piece is 50 ° C. to 200 ° C.
° C and the resistance value of the low melting point fusible alloy piece is 0.1
The alloy-type temperature fuse according to any one of claims 1 to 3, wherein the temperature is in the range of -400 mΩ. 5. The alloy type temperature fuse according to claim 1, which is attached in contact with the secondary battery.